Zhang Yan, Yao Yi-Fan, Qiao Yuan-Yuan, Wang Gui-Chang
Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and the Tianjin Key Lab and Molecule-based Material Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.
Phys Chem Chem Phys. 2021 Jan 6;23(1):617-627. doi: 10.1039/d0cp04732e.
The entire reaction mechanism of the dry reforming of methane (DRM) as well as the competition processes over perfect and boron-vacancy-containing h-BN sheet-supported Ni-catalysts (labeled Ni2/h-BN and Ni2/h-BN-B-D) was studied by density functional theory calculations in the present work. Our calculation results show that B-defected h-BN strongly binds to the Ni2 active sites (i.e., shows a strong metal-support interaction (SMSI) character) due to the better electron transfer between Ni2 sites and the support. It was found that CH4 is easier to activate than molecular CO2. The activation of CO2 occurs on the surface of Ni2/h-BN through a direct route, whereas it is prone to follow a hydrogen-assisted path for Ni2/h-BN-B-D via the COOH* intermediate, and the results show that the oxidant O* is easily formed on the surface of Ni2/h-BN-B-D. It was also found that O* is the main oxidant agent for CHx* intermediates through the CH3-O oxidation mechanism. The reaction kinetic analysis indicated that the reverse water gas shift reaction (RWGS) is much more favorable than DRM (1.30 vs. 1.72 eV) over the Ni2/h-BN system, whereas the RWGS and DRM are comparable on Ni2/h-BN-B-D (1.77 vs. 1.66 eV), suggesting a high DRM activity on Ni2/h-BN-B-D. Moreover, neither methane cracking nor a Boudouard reaction to form C* species is thermodynamically and kinetically unfavorable over Ni2/h-BN-B-D; hence, Ni2/h-BN-B-D has strong resistance to carbon deposition. Compared to Ni(111), both Ni2/h-BN-B-D and Ni2/h-BN show strong resistance to carbon deposition. Our results provide a further mechanistic understanding of the DRM over an Ni-based catalyst through the SMSI characteristic and the SMSI favors strong resistance to carbon deposition.
在本工作中，通过密度泛函理论计算研究了甲烷干重整（DRM）的整个反应机理以及在完美的和含硼空位的h-BN片负载的Ni催化剂（标记为Ni2/h-BN和Ni2/h-BN-B-D）上的竞争过程。我们的计算结果表明，由于Ni2位点与载体之间更好的电子转移，缺硼的h-BN与Ni2活性位点强烈结合（即表现出强金属-载体相互作用（SMSI）特征）。研究发现，CH4比分子CO2更容易被活化。CO2的活化通过直接途径在Ni2/h-BN表面发生，而对于Ni2/h-BN-B-D，它倾向于通过COOH中间体遵循氢辅助路径，结果表明在Ni2/h-BN-B-D表面容易形成氧化剂O。还发现O通过CH3-O氧化机理是CHx中间体的主要氧化剂。反应动力学分析表明，在Ni2/h-BN体系上，逆水煤气变换反应（RWGS）比DRM更有利（1.30对1.72 eV），而在Ni2/h-BN-B-D上RWGS和DRM相当（1.77对1.66 eV），这表明Ni2/h-BN-B-D具有高DRM活性。此外，在Ni2/h-BN-B-D上，甲烷裂解和形成C*物种的布多阿尔反应在热力学和动力学上都不利；因此，Ni2/h-BN-B-D具有很强的抗积碳能力。与Ni(111)相比，Ni2/h-BN-B-D和Ni2/h-BN都表现出很强的抗积碳能力。我们的结果通过SMSI特性对基于Ni的催化剂上的DRM提供了进一步的机理理解，并且SMSI有利于强抗积碳能力。
